In wire-cut electric discharge machining, products of various shapes are produced by moving a table mounted with a workpiece, while intermittently generating electric discharge between a wire traveling from an upper nozzle toward a lower nozzle and the workpiece located between these nozzles. In the case of cutting-out, from a single workpiece, a plurality of pieces each constituting a product or a core corresponding to a cavity portion of the product, the workpiece is moved to a cutting-out machining start position for the next piece each time the cutting-out machining for one of the pieces is completed. At this time, the cut-out piece and the lower nozzle may be rubbed against each other, resulting in damage to the cut-out piece or the lower nozzle, in particular, if the workpiece is moved under a condition that the cut-out piece is inclined in the workpiece due to its own weight. If the cut-out piece as a product incurs a frictional scratch, the product quality is deteriorated.
To obviate these inconveniences, it has been known to remove cut-out pieces from a workpiece by means of various methods each time one of the cut-out pieces is cut out from the workpiece. For instance, a workpiece is horizontally moved while a cut-out piece is held in the workpiece with the aid of a supporting plate extending between the bottom surface of the workpiece and the upper end surface of the lower nozzle, and the natural falling of the cut-out piece from the supporting plate and the workpiece is permitted at the end of the supporting plate at a location separated from the lower nozzle in the horizontal direction. This method is easy to implement, but if the top surface of the supporting plate is soiled or scratched, then the movement of the piece on the supporting plate and hence the movement of the workpiece may be prevented, possibly causing scratches on the piece or undue load onto a table driving mechanism which moves the workpiece.
Another method is known, wherein a piece which is not completely cut out of but left slightly linked to the workpiece is tapped off the workpiece with a hammer or the like. This method, however, is likely to easily cause a flaw on the piece. Further, if the hammer is made smaller so that it can remove even such a piece which is small in horizontal section, then it may fail to remove a piece having a larger horizontal section or a greater thickness.
Still another method is known, wherein a cut-out piece, which is drawn up out of a workpiece using a suction means, such as magnet, suction pad, etc. is moved, with the piece attached to the suction means, to a position horizontally away from the lower nozzle, and then the sucking action of the suction means is released so as to detach the cut-out piece at that position. Further, another method is known, wherein a cut-out piece held in a workpiece using a similar suction means is moved in unison with the workpiece to a position away from the lower nozzle, and then the suction of the suction means is released to permit the natural falling of the cut-out piece. However, an electromagnetic suction means such as magnet cannot be applied to cut-out pieces made of non-magnetic materials. In the case of using a suction pad or the like, the provision of a complicated piping is required to connect the suction pad or the like to a pressure reducing device. Also, a cut-out piece, which has a limited effective suction area because of its rugged top surface or other reasons, is likely to come off suction means during the movement. When a cut-out piece is removed from the workpiece by drawing it up, part of the main body of an electric discharge machine to which suction means is installed must be reinforced. When a cut-out piece is moved in unison with the workpiece, the suction means must be moved in synchronization with the movement of the workpiece, resulting in a complicated device configuration.